1. Field of the Invention
The present invention relates to a manufacturing method of a hermetic container. In particular, the present invention relates to a manufacturing method of a hermetic container, the inside of which has been vacuumized and which holds therein an electron-emitting device and a phosphor film.
2. Description of the Related Art
Conventionally, image displaying apparatuses of a flat panel type such as an organic LED (light-emitting diode) display (OLED), a field emission display (FED), a plasma display panel (PDP), and the like are well known. Each of these image displaying apparatuses is manufactured by hermetically sealing glass substrates facing each other, and has a container (hermetic container) in which the internal space is partitioned to an external space. To manufacture the hermetic container like this, a spacing distance defining member, a local adhesive and the like are arranged between the facing glass substrates as necessary, a sealing material is arranged in a frame shape to the peripheral portions of the glass substrates, and then a heat sealing process is performed. Here, as a sealing material heating method in the heat sealing process, a method whereby the whole glass substrates are baked by a furnace (whole heating), and a method whereby the substrate is locally heated along the sealing material (local heating) are known. Generally, the local heating is more advantageous than the whole heating from viewpoints of a time which is required to heat and cool, an energy which is required to heat, productivity, prevention of thermal deformation of the container, prevention of thermal deterioration of a function device arranged in the container, and the like. In particular, a laser beam is known as a means for the local heating.
Japanese Patent Application Laid-Open (Translation of PCT International Publication) No. 2002-515392 discloses a manufacturing method of a container of a flat panel display, which includes a method of forming a glass frit bar serving as a sealing material. The glass frit bar has a concavo-convex shape so as to improve airtightness at the outer peripheral portion of the flat panel display. In this method, the peripheral portion and the glass frit bar are fitted together and heated to melt the glass frit bar, whereby the flat panel display which is inexpensive and highly reliable for a long time can be manufactured.
Japanese Patent Application Laid-Open No. 2007-234334 discloses a manufacturing method of a container of an image displaying apparatus. In the manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2007-234334, respective fitting portions (sealing portions) of plural frame members are sealed by using high melting point frit, whereby a joined frame body is constituted. Then, the frame body is set between a rear substrate and a front substrate, and the rear substrate, the front substrate and the frame body are sealed by low melting point frit.
Japanese Patent Application Laid-Open No. H09-208270 discloses a manufacturing method of double-glazed glass. In this method, a pair of glass plates and a frame body disposed between the glass plates are adhered by induction heating using high-frequency wave or microwave in which a difference between a dielectric loss of an adhesive and a dielectric loss of the glass plate and/or the frame body is used.
As described above, the method of manufacturing the hermetic container by joining the plural frame members like a frame to constitute the frame body and then sealing the frame body to the pair of the substrates is known. However, in case of generating, by using local heating light as a heating means, an amount of heat necessary to melt and soften the sealing material to obtain a sufficient joining strength, there is a case where a distortion occurs in the hermetic container. By this distortion, there are fears that the strength and the airtightness of the hermetic container decrease and the misalignment between the pair of the substrates occurs. This is because a temperature difference occurs between the pair of the substrates and the frame body due to the local heating light, and a difference occurs between the expansion/contraction amounts of the pair of the substrates and the frame body due to the temperature difference. In particular, when the local heating light is scanned along the frame body, the expansion/contraction amount of the frame body accumulates at the irradiation end portion of the local heating light. When the portion of the already-sealed frame body is present at the irradiation end portion of the local heating light, a distortion occurs between the irradiation end portion and the already-sealed portion, and this distortion becomes a factor for deteriorating the joining strength and the airtightness of the hermetic container.
The present invention aims to provide a hermetic container manufacturing method by which the joining strength and the airtightness of the hermetic container can be improved.